The invention relates to a method and a device for controlling the position of bore bushings in drilling templates which are used in the field of tooth implantation and serve to guide a drill which is used to create bores in a patient's jaw, for anchoring implants in these.
Drilling templates of this type are generally produced in the following way: First, a dentist takes an impression of a patient's jaw. The impression is used to produce a plaster model for creating a bite splint. The latter is worn by the patient while his jaw is recorded by computed tomography in order to permit a three-dimensional implant plan. To ensure that the plan can be transposed back to the patient, the drilling template typically contains registration markings. This plan ensures that the implants are disposed in the jaw bone such that, when creating the required bores for the implants, no nerves are damaged and there is no perforation of the paranasal sinuses. After establishing the course and arrangement of the drill channels and the drilling depth in the jaw bone, bore bushings are introduced into the bite splint. These preferably are made of titanium and are arranged such that they can be used to guide a drill with which the planned drill channels can be formed in the jaw. The angle disposition of the bore bushings is used to allow the drill channel to be formed at the desired orientation in the jaw bone. The drilling depth is fixed by the bore bushing edge which serves as an abutment for the drill and which surrounds the bushing inlet into which a drill is later inserted.
The bite splint which is provided with the bore bushings, and which now serves as a drilling template, is fitted in a patient who is to receive one or more implants. The bore bushings fixed in the bite splint or drilling template now act as a mechanical guide for the operator, and as an abutment for a drill with which holes are formed in the jaw in order to receive implants.
It has been found that, when introducing bore bushings into the bite splint, i.e. when producing the drilling template, deviations from the plan may arise in the positions of the bore bushings, e.g. as a result of human operating errors. Moreover, the bore bushings may be incorrectly axially introduced wrongly into the bite splint serving as the drilling template. The operator may be able to notice obvious errors from the arrangement of the bore bushings and by comparison with the images created by means of computed tomography. But, of course, not all errors can be picked up in this way, and so patients are endangered to the extent that the orientation of the bores formed in the jaw for the implants and the depth of the bores are sometimes determined incorrectly.
In the text below, “position” is understood, in each case with respect to a defined coordinate system, as the parameter values of the 6 degrees of freedom of a rigid object in three-dimensional space.
In a rotationally symmetrical bushing, the position is accordingly described unambiguously by 5 parameters.
A derived position parameter is obtained by conversion from parameter values of another coordinate system or by projection of the parameter values into a new coordinate system.
The terms “angle position and/or axial position” are used here synonymously for position parameters or for a subset of position parameters.